Current Grants

• Solar Wind Electrons Alphas and Protons (SWEAP): NASA's Parker Solar Probe mission Co-I
• Improved Characterization of Solar Wind Dissipation, Energization, and Stability, NASA Heliophysics Early Career Investigator Program
• Non-Maxwellian Distribution Functions in the Solar Wind: Dispersion Relations and Instabilities, NASA Heliophysics Supporting Research Program
• Investigation of Electron Parameter Statistical Distributions and Association with Structures using QTN Spectroscopy
• Vlasov-Maxwell Simulations to Resolve Electron Heating and Dissipation in Quasi-Perpendicular Shocks- NSF-DOE Basic Plasma Physics Partnership
• Hybrid Kinetic-GRMHD simulations of Black Hole Accretion with Data-Calibrated Electron Physics, NASA Astrophysics Theory Program
• Coupling of Electron and Ion Kinetic Physics via Collisions and Instabilities in the Expanding Solar Wind, NASA Heliophysics Supporting Research
• Parametric Instability in the Inner Heliosphere, NASA Heliophysics Supporting Research Grant

Current Spacecraft Involvement

• HelioSwarm
• Parker Solar Probe
• Wind

Current Graduate Students

• Niranjana Shankarappa (Physics)

Current Postdocs

• Emily Lichko

Former Postdocs

• Mihailo Martinović

Complete publications list available from: NASA ADS Author search: Kristopher G. Klein (See also ORCID 0000-0001-6038-1923)

Recent refereed publications (NASA ADS): Years 2019 through June 2022

Martinović, Mihailo M., Dordević, Antonije R., Klein, Kristopher G., Maksimović, Milan, Issautier, Karine, Liu, Mingzhe, Pulupa, Marc, Bale, Stuart D., Halekas, Jasper S., & McManus, Michael D. 2022, Journal of Geophysical Research (Space Physics). Plasma Parameters From Quasi-Thermal Noise Observed by Parker Solar Probe: A New Model for the Antenna Response

Verniero, J. L., Chandran, B. D. G., Larson, D. E., Paulson, K., Alterman, B. L., Badman, S., Bale, S. D., Bonnell, J. W., Bowen, T. A., de Wit, T. Dudok, Kasper, J. C., Klein, K. G., Lichko, E., Livi, R., McManus, M. D., Rahmati, A., Verscharen, D., Walters, J., & Whittlesey, P. L. 2022, The Astrophysical Journal. Strong Perpendicular Velocity-space Diffusion in Proton Beams Observed by Parker Solar Probe

Martinović, Mihailo M., Klein, Kristopher G., Ďurovcová, Tereza, & Alterman, Benjamin L. 2021, The Astrophysical Journal. Ion-driven Instabilities in the Inner Heliosphere. I. Statistical Trends

Esman, T. M., Espley, J., Gruesbeck, J., Klein, K. G., & Giacalone, J. 2021, Journal of Geophysical Research (Space Physics). Plasma Waves in the Distant Martian Environment: Implications for Mars' Sphere of Influence

Vech, Daniel, Malaspina, David M., Cattell, Cynthia, Schwartz, Steven J., Ergun, Robert E., Klein, Kristopher G., Kromyda, Lily, & Chasapis, Alexandros 2021, Journal of Geophysical Research (Space Physics). Experimental Determination of Ion Acoustic Wave Dispersion Relation With Interferometric Analysis

Broeren, T., Klein, K. G., TenBarge, J. M., Dors, Ivan, Roberts, O. W., & Verscharen, D. 2021, Frontiers in Astronomy and Space Sciences. Magnetic Field Reconstruction for a Realistic Multi-Point, Multi-Scale Spacecraft Observatory

Juno, James, Howes, Gregory G., TenBarge, Jason M., Wilson, Lynn B., Spitkovsky, Anatoly, Caprioli, Damiano, Klein, Kristopher G., & Hakim, Ammar 2021, Journal of Plasma Physics. A field-particle correlation analysis of a perpendicular magnetized collisionless shock

Verscharen, Daniel, Wicks, Robert T., Alexandrova, Olga, Bruno, Roberto, Burgess, David, Chen, Christopher H. K., D'Amicis, Raffaella, De Keyser, Johan, de Wit, Thierry Dudok, Franci, Luca, He, Jiansen, Henri, Pierre, Kasahara, Satoshi, Khotyaintsev, Yuri, Klein, Kristopher G., Lavraud, Benoit, Maruca, Bennett A., Maksimovic, Milan, Plaschke, Ferdinand, Poedts, Stefaan, Reynolds, Christopher S., Roberts, Owen, Sahraoui, Fouad, Saito, Shinji, Salem, Chadi S., Saur, Joachim, Servidio, Sergio, Stawarz, Julia E., Štverák, Štěpán, & Told, Daniel 2021, Experimental Astronomy. A Case for Electron-Astrophysics

Vech, D., Stevens, M. L., Paulson, K. W., Malaspina, D. M., Case, A. W., Klein, K. G., & Kasper, J. C. 2021, Astronomy and Astrophysics. A powerful machine learning technique to extract proton core, beam, and α-particle parameters from velocity distribution functions in space plasmas

Halekas, J. S., Whittlesey, P. L., Larson, D. E., McGinnis, D., Bale, S. D., Berthomier, M., Case, A. W., Chandran, B. D. G., Kasper, J. C., Klein, K. G., Korreck, K. E., Livi, R., MacDowall, R. J., Maksimovic, M., Malaspina, D. M., Matteini, L., Pulupa, M. P., & Stevens, M. L. 2021, Astronomy and Astrophysics. Electron heat flux in the near-Sun environment

Verniero, J. L., Howes, G. G., Stewart, D. E., & Klein, K. G. 2021, Journal of Geophysical Research (Space Physics). PATCH: Particle Arrival Time Correlation for Heliophysics

Verniero, J. L., Howes, G. G., Stewart, D. E., & Klein, K. G. 2021, Journal of Geophysical Research (Space Physics). Determining Threshold Instrumental Resolutions for Resolving the Velocity Space Signature of Ion Landau Damping

Klein, K. G., Verniero, J. L., Alterman, B., Bale, S., Case, A., Kasper, J. C., Korreck, K., Larson, D., Lichko, E., Livi, R., McManus, M., Martinović, M., Rahmati, A., Stevens, M., & Whittlesey, P. 2021, The Astrophysical Journal. Inferred Linear Stability of Parker Solar Probe Observations Using One- and Two-component Proton Distributions

Chen, C. H. K., Chandran, B. D. G., Woodham, L. D., Jones, S. I., Perez, J. C., Bourouaine, S., Bowen, T. A., Klein, K. G., Moncuquet, M., Kasper, J. C., Bale, S. D. 2021, Astronomy and Astrophysics The near-Sun streamer belt solar wind: turbulence and solar wind acceleration

Vech, D., Martinović, M. M., Klein, K. G., Malaspina, D. M., Bowen, T. A., Verniero, J. L., Paulson, K., Dudok de Wit, T., Kasper, J. C., Huang, J., Stevens, M. L., Case, A. W., Korreck, K., Mozer, F. S., Goodrich, K. A., Bale, S. D., Whittlesey, P. L., Livi, R., Larson, D. E., Pulupa, M., Bonnell, J., Harvey, P., Goetz, K., MacDowall, R. 2021, Astronomy and Astrophysics Wave-particle energy transfer directly observed in an ion cyclotron wave

Zhao, L.-L., Zank, G. P., Hu, Q., Telloni, D., Chen, Y., Adhikari, L., Nakanotani, M., Kasper, J. C., Huang, J., Bale, S. D., Korreck, K. E., Case, A. W., Stevens, M., Bonnell, J. W., Dudok de Wit, T., Goetz, K., Harvey, P. R., MacDowall, R. J., Malaspina, D. M., Pulupa, M., Larson, D. E., Livi, R., Whittlesey, P., Klein, K. G., Raouafi, N. E. 2021, Astronomy and Astrophysics Detection of small magnetic flux ropes from the third and fourth Parker Solar Probe encounters

Martinović, M. M., Klein, K. G., Huang, J., Chandran, B. D. G., Kasper, J. C., Lichko, E., Bowen, T., Chen, C. H. K., Matteini, L., Stevens, M., Case, A. W., Bale, S. D. 2021, The Astrophysical Journal Multiscale Solar Wind Turbulence Properties inside and near Switchbacks Measured by the Parker Solar Probe

Perez, J. C., Chandran, B. D. G., Klein, K. G., Martinović, M. M. 2021, Journal of Plasma Physics How Alfvén waves energize the solar wind: heat versus work

Bourouaine, Sofiane, Perez, Jean C., Klein, Kristopher G., Chen, Christopher H. K., Martinović, Mihailo, Bale, Stuart D., Kasper, Justin C., & Raouafi, Nour E. 2020, The Astrophysical Journal. Turbulence Characteristics of Switchback and Nonswitchback Intervals Observed by Parker Solar Probe

Woolley, Thomas, Matteini, Lorenzo, Horbury, Timothy S., Bale, Stuart D., Woodham, Lloyd D., Laker, Ronan, Alterman, Benjamin L., Bonnell, John W., Case, Anthony W., Kasper, Justin C., Klein, Kristopher G., Martinović, Mihailo M., & Stevens, Michael 2020, Monthly Notices of the Royal Astronomical Society. Proton core behaviour inside magnetic field switchbacks

Chen, Yu, Hu, Qiang, Zhao, Lingling, Kasper, Justin C., Bale, Stuart D., Korreck, Kelly E., Case, Anthony W., Stevens, Michael L., Bonnell, John W., Goetz, Keith, Harvey, Peter R., Klein, Kristopher G., Larson, Davin E., Livi, Roberto, MacDowall, Robert J., Malaspina, David M., Pulupa, Marc, & Whittlesey, Phyllis L. 2020, The Astrophysical Journal. Small-scale Magnetic Flux Ropes in the First Two Parker Solar Probe Encounters

Kawazura, Y., Schekochihin, A. A., Barnes, M., TenBarge, J. M., Tong, Y., Klein, K. G., & Dorland, W. 2020, Physical Review X. Ion versus Electron Heating in Compressively Driven Astrophysical Gyrokinetic Turbulence

Klein, Kristopher G., Howes, Gregory G., TenBarge, Jason M., & Valentini, Francesco 2020, Journal of Plasma Physics. Diagnosing collisionless energy transfer using field-particle correlations: Alfvén-ion cyclotron turbulence

Martinović, Mihailo M., Klein, Kristopher G., Gramze, Savannah R., Jain, Himanshu, Maksimović, Milan, Zaslavsky, Arnaud, Salem, Chadi, Zouganelis, Ioannis, & Simić, Zoran 2020, Journal of Geophysical Research (Space Physics). Solar Wind Electron Parameters Determination on Wind Spacecraft Using Quasi-Thermal Noise Spectroscopy

Verscharen, Daniel, Parashar, Tulasi N., Gary, S. Peter, & Klein, Kristopher G. 2020, Monthly Notices of the Royal Astronomical Society. Dependence of kinetic plasma waves on ion-to-electron mass ratio and light-to-Alfvén speed ratio

Verniero, J. L., Larson, D. E., Livi, R., Rahmati, A., McManus, M. D., Pyakurel, P. Sharma, Klein, K. G., Bowen, T. A., Bonnell, J. W., Alterman, B. L., Whittlesey, P. L., Malaspina, David M., Bale, S. D., Kasper, J. C., Case, A. W., Goetz, K., Harvey, P. R., Korreck, K. E., MacDowall, R. J., Pulupa, M., Stevens, M. L., & de Wit, T. Dudok 2020, The Astrophysical Journal Supplement Series. Parker Solar Probe Observations of Proton Beams Simultaneous with Ion-scale Waves

Lavraud, B., Fargette, N., Réville, V., Szabo, A., Huang, J., Rouillard, A. P., Viall, N., Phan, T. D., Kasper, J. C., Bale, S. D., Berthomier, M., Bonnell, J. W., Case, A. W., Dudok de Wit, T., Eastwood, J. P., Génot, V., Goetz, K., Griton, L. S., Halekas, J. S., Harvey, P., Kieokaew, R., Klein, K. G., Korreck, K. E., Kouloumvakos, A., Larson, D. E., Lavarra, M., Livi, R., Louarn, P., MacDowall, R. J., Maksimovic, M., Malaspina, D., Nieves-Chinchilla, T., Pinto, R. F., Poirier, N., Pulupa, M., Raouafi, N. E., Stevens, M. L., Toledo-Redondo, S., & Whittlesey, P. L. 2020, The Astrophysical Journal. The Heliospheric Current Sheet and Plasma Sheet during Parker Solar Probe's First Orbit

Whittlesey, Phyllis L., Larson, Davin E., Kasper, Justin C., Halekas, Jasper, Abatcha, Mamuda, Abiad, Robert, Berthomier, M., Case, A. W., Chen, Jianxin, Curtis, David W., Dalton, Gregory, Klein, Kristopher G., Korreck, Kelly E., Livi, Roberto, Ludlam, Michael, Marckwordt, Mario, Rahmati, Ali, Robinson, Miles, Slagle, Amanda, Stevens, M. L., Tiu, Chris, & Verniero, J. L. 2020, The Astrophysical Journal Supplement Series. The Solar Probe ANalyzers—Electrons on the Parker Solar Probe

Huang, Jia, Kasper, J. C., Vech, D., Klein, K. G., Stevens, M., Martinović, Mihailo M., Alterman, B. L., Ďurovcová, Tereza, Paulson, Kristoff, Maruca, Bennett A., Qudsi, Ramiz A., Case, A. W., Korreck, K. E., Jian, Lan K., Velli, Marco, Lavraud, B., Hegedus, A., Bert, C. M., Holmes, J., Bale, Stuart D., Larson, Davin E., Livi, Roberto, Whittlesey, P., Pulupa, Marc, MacDowall, Robert J., Malaspina, David M., Bonnell, John W., Harvey, Peter, Goetz, Keith, & Dudok de Wit, Thierry 2020, The Astrophysical Journal Supplement Series. Proton Temperature Anisotropy Variations in Inner Heliosphere Estimated with the First Parker Solar Probe Observations

Bowen, Trevor A., Mallet, Alfred, Huang, Jia, Klein, Kristopher G., Malaspina, David M., Stevens, Michael, Bale, Stuart D., Bonnell, J. W., Case, Anthony W., Chandran, Benjamin D. G., Chaston, C. C., Chen, Christopher H. K., Dudok de Wit, Thierry, Goetz, Keith, Harvey, Peter R., Howes, Gregory G., Kasper, J. C., Korreck, Kelly E., Larson, Davin, Livi, Roberto, MacDowall, Robert J., McManus, Michael D., Pulupa, Marc, Verniero, J. L., & Whittlesey, Phyllis 2020, The Astrophysical Journal Supplement Series. Ion-scale Electromagnetic Waves in the Inner Heliosphere

Chen, C. H. K., Bale, S. D., Bonnell, J. W., Borovikov, D., Bowen, T. A., Burgess, D., Case, A. W., Chandran, B. D. G., de Wit, T. Dudok, Goetz, K., Harvey, P. R., Kasper, J. C., Klein, K. G., Korreck, K. E., Larson, D., Livi, R., MacDowall, R. J., Malaspina, D. M., Mallet, A., McManus, M. D., Moncuquet, M., Pulupa, M., Stevens, M. L., & Whittlesey, P. 2020, The Astrophysical Journal Supplement Series. The Evolution and Role of Solar Wind Turbulence in the Inner Heliosphere

Vech, Daniel, Kasper, Justin C., Klein, Kristopher G., Huang, Jia, Stevens, Michael L., Chen, Christopher H. K., Case, Anthony W., Korreck, Kelly, Bale, Stuart D., Bowen, Trevor A., Whittlesey, Phyllis L., Livi, Roberto, Larson, Davin E., Malaspina, David, Pulupa, Marc, Bonnell, John, Harvey, Peter, Goetz, Keith, Dudok de Wit, Thierry, & MacDowall, Robert 2020, The Astrophysical Journal Supplement Series. Kinetic-scale Spectral Features of Cross Helicity and Residual Energy in the Inner Heliosphere

Bandyopadhyay, Riddhi, Goldstein, M. L., Maruca, B. A., Matthaeus, W. H., Parashar, T. N., Ruffolo, D., Chhiber, R., Usmanov, A., Chasapis, A., Qudsi, R., Bale, Stuart D., Bonnell, J. W., Dudok de Wit, Thierry, Goetz, Keith, Harvey, Peter R., MacDowall, Robert J., Malaspina, David M., Pulupa, Marc, Kasper, J. C., Korreck, K. E., Case, A. W., Stevens, M., Whittlesey, P., Larson, D., Livi, R., Klein, K. G., Velli, M., & Raouafi, N. 2020, The Astrophysical Journal Supplement Series. Enhanced Energy Transfer Rate in Solar Wind Turbulence Observed near the Sun from Parker Solar Probe

Horbury, Timothy S., Woolley, Thomas, Laker, Ronan, Matteini, Lorenzo, Eastwood, Jonathan, Bale, Stuart D., Velli, Marco, Chandran, Benjamin D. G., Phan, Tai, Raouafi, Nour E., Goetz, Keith, Harvey, Peter R., Pulupa, Marc, Klein, K. G., Dudok de Wit, Thierry, Kasper, Justin C., Korreck, Kelly E., Case, A. W., Stevens, Michael L., Whittlesey, Phyllis, Larson, Davin, MacDowall, Robert J., Malaspina, David M., & Livi, Roberto 2020, The Astrophysical Journal Supplement Series. Sharp Alfvénic Impulses in the Near-Sun Solar Wind

Case, A. W., Kasper, Justin C., Stevens, Michael L., Korreck, Kelly E., Paulson, Kristoff, Daigneau, Peter, Caldwell, Dave, Freeman, Mark, Henry, Thayne, Klingensmith, Brianna, Bookbinder, J. A., Robinson, Miles, Berg, Peter, Tiu, Chris, Wright, K. H., Reinhart, Matthew J., Curtis, David, Ludlam, Michael, Larson, Davin, Whittlesey, Phyllis, Livi, Roberto, Klein, Kristopher G., & Martinović, Mihailo M. 2020, The Astrophysical Journal Supplement Series. The Solar Probe Cup on the Parker Solar Probe

Kim, T. K., Pogorelov, N. V., Arge, C. N., Henney, C. J., Jones-Mecholsky, S. I., Smith, W. P., Bale, S. D., Bonnell, J. W., Dudok de Wit, T., Goetz, K., Harvey, P. R., MacDowall, R. J., Malaspina, D. M., Pulupa, M., Kasper, J. C., Korreck, K. E., Stevens, M., Case, A. W., Whittlesey, P., Livi, R., Larson, D. E., Klein, K. G., & Zank, G. P. 2020, The Astrophysical Journal Supplement Series. Predicting the Solar Wind at the Parker Solar Probe Using an Empirically Driven MHD Model

Adhikari, L., Zank, G. P., Zhao, L. -L., Kasper, J. C., Korreck, K. E., Stevens, M., Case, A. W., Whittlesey, P., Larson, D., Livi, R., & Klein, K. G. 2020, The Astrophysical Journal Supplement Series. Turbulence Transport Modeling and First Orbit Parker Solar Probe (PSP) Observations

Tenerani, Anna, Velli, Marco, Matteini, Lorenzo, Réville, Victor, Shi, Chen, Bale, Stuart D., Kasper, Justin C., Bonnell, John W., Case, Anthony W., de Wit, Thierry Dudok, Goetz, Keith, Harvey, Peter R., Klein, Kristopher G., Korreck, Kelly, Larson, Davin, Livi, Roberto, MacDowall, Robert J., Malaspina, David M., Pulupa, Marc, Stevens, Michael, & Whittlesey, Phyllis 2020, The Astrophysical Journal Supplement Series. Magnetic Field Kinks and Folds in the Solar Wind

Martinović, Mihailo M., Klein, Kristopher G., Kasper, Justin C., Case, Anthony W., Korreck, Kelly E., Larson, Davin, Livi, Roberto, Stevens, Michael, Whittlesey, Phyllis, Chandran, Benjamin D. G., Alterman, Ben L., Huang, Jia, Chen, Christopher H. K., Bale, Stuart D., Pulupa, Marc, Malaspina, David M., Bonnell, John W., Harvey, Peter R., Goetz, Keith, Dudok de Wit, Thierry, & MacDowall, Robert J. 2020, The Astrophysical Journal Supplement Series. The Enhancement of Proton Stochastic Heating in the Near-Sun Solar Wind

Giacalone, J., Mitchell, D. G., Allen, R. C., Hill, M. E., McNutt, R. L., Szalay, J. R., Desai, M. I., Rouillard, A. P., Kouloumvakos, A., McComas, D. J., Christian, E. R., Schwadron, N. A., Wiedenbeck, M. E., Bale, S., Brown, L. E., Case, A., Chen, X., Cohen, C. M. S., Joyce, C., Kasper, J. C., Klein, K. G., Korreck, K., Larson, D. E., Livi, R., Leske, R. A., MacDowall, R. J., Matthaeus, W. H., Mewaldt, R. A., Nieves-Chinchilla, T., Pulupa, M., Roelof, E. C., Stevens, M. L., Szabo, A., & Whittlesey, P. L. 2020, The Astrophysical Journal Supplement Series. Solar Energetic Particles Produced by a Slow Coronal Mass Ejection at ∼0.25 au

Zhao, L. -L., Zank, G. P., Adhikari, L., Hu, Q., Kasper, J. C., Bale, S. D., Korreck, K. E., Case, A. W., Stevens, M., Bonnell, J. W., Dudok de Wit, T., Goetz, K., Harvey, P. R., MacDowall, R. J., Malaspina, D. M., Pulupa, M., Larson, D. E., Livi, R., Whittlesey, P., & Klein, K. G. 2020, The Astrophysical Journal Supplement Series. Identification of Magnetic Flux Ropes from Parker Solar Probe Observations during the First Encounter

Halekas, J. S., Whittlesey, P., Larson, D. E., McGinnis, D., Maksimovic, M., Berthomier, M., Kasper, J. C., Case, A. W., Korreck, K. E., Stevens, M. L., Klein, K. G., Bale, S. D., MacDowall, R. J., Pulupa, M. P., Malaspina, D. M., Goetz, K., & Harvey, P. R. 2020, The Astrophysical Journal Supplement Series. Electrons in the Young Solar Wind: First Results from the Parker Solar Probe

Kasper, J. C., Bale, S. D., Belcher, J. W., Berthomier, M., Case, A. W., Chandran, B. D. G., Curtis, D. W., Gallagher, D., Gary, S. P., Golub, L., Halekas, J. S., Ho, G. C., Horbury, T. S., Hu, Q., Huang, J., Klein, K. G., Korreck, K. E., Larson, D. E., Livi, R., Maruca, B., Lavraud, B., Louarn, P., Maksimovic, M., Martinovic, M., McGinnis, D., Pogorelov, N. V., Richardson, J. D., Skoug, R. M., Steinberg, J. T., Stevens, M. L., Szabo, A., Velli, M., Whittlesey, P. L., Wright, K. H., Zank, G. P., MacDowall, R. J., McComas, D. J., McNutt, R. L., Pulupa, M., Raouafi, N. E., & Schwadron, N. A. 2019, Nature. Alfvénic velocity spikes and rotational flows in the near-Sun solar wind

Verscharen, Daniel, Klein, Kristopher G., & Maruca, Bennett A. 2019, Living Reviews in Solar Physics. The multi-scale nature of the solar wind

Klein, Kristopher G., Martinović, Mihailo, Stansby, David, & Horbury, Timothy S. 2019, The Astrophysical Journal. Linear Stability in the Inner Heliosphere: Helios Re-evaluated

Li, Tak Chu, Howes, Gregory G., Klein, Kristopher G., Liu, Yi-Hsin, & Tenbarge, Jason M. 2019, Journal of Plasma Physics. Collisionless energy transfer in kinetic turbulence: field-particle correlations in Fourier space

Martinović, Mihailo M., Klein, Kristopher G., & Bourouaine, Sofiane 2019, The Astrophysical Journal. Radial Evolution of Stochastic Heating in Low-β Solar Wind

Mallet, Alfred, Klein, Kristopher G., Chandran, Benjamin D. G., Grošelj, Daniel, Hoppock, Ian W., Bowen, Trevor A., Salem, Chadi S., & Bale, Stuart D. 2019, Journal of Plasma Physics. Interplay between intermittency and dissipation in collisionless plasma turbulence

Kasper, Justin C. & Klein, Kristopher G. 2019, The Astrophysical Journal. Strong Preferential Ion Heating is Limited to within the Solar Alfvén Surface

Chen, C. H. K., Klein, K. G., & Howes, G. G. 2019, Nature Communications. Evidence for electron Landau damping in space plasma turbulence

van der Holst, B., Manchester, W. B., Klein, K. G., & Kasper, J. C. 2019, The Astrophysical Journal. Predictions for the First Parker Solar Probe Encounter