Ion Scale Electromagnetic Waves in the Inner Heliosphere. (arXiv:1912.02361v1 [astro-ph.SR])

Ion Scale Electromagnetic Waves in the Inner Heliosphere. (arXiv:1912.02361v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Bowen_T/0/1/0/all/0/1">Trevor Bowen</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mallet_A/0/1/0/all/0/1">Alfred Mallet</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Huang_J/0/1/0/all/0/1">Jia Huang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Klein_K/0/1/0/all/0/1">Kristopher G. Klein</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Malaspina_D/0/1/0/all/0/1">David M. Malaspina</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Stevens_M/0/1/0/all/0/1">Michael L. Stevens</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bale_S/0/1/0/all/0/1">Stuart D. Bale</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bonnell_J/0/1/0/all/0/1">John W. Bonnell</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Case_A/0/1/0/all/0/1">Anthony W. Case</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Chandran_B/0/1/0/all/0/1">Benjamin D. Chandran</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Chaston_C/0/1/0/all/0/1">Christopher Chaston</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Chen_C/0/1/0/all/0/1">Christopher H. Chen</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wit_T/0/1/0/all/0/1">Thierry Dudok de Wit</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Goetz_K/0/1/0/all/0/1">Keith Goetz</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Harvey_P/0/1/0/all/0/1">Peter R. Harvey</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Howes_G/0/1/0/all/0/1">Gregory G. Howes</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kasper_J/0/1/0/all/0/1">Justin C. Kasper</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Korreck_K/0/1/0/all/0/1">Kelly Korreck</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Larson_D/0/1/0/all/0/1">Davin E. Larson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Livi_R/0/1/0/all/0/1">Roberto Livi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+MacDowall_R/0/1/0/all/0/1">Robert J. MacDowall</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+McManus_M/0/1/0/all/0/1">Michael McManus</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pulupa_M/0/1/0/all/0/1">Marc Pulupa</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Verniero_J/0/1/0/all/0/1">J Verniero</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Whittlesey_P/0/1/0/all/0/1">Phyllis Whittlesey</a>

Understanding the physical processes in the solar wind and corona which
actively contribute to heating, acceleration, and dissipation is a primary
objective of NASA’s Parker Solar Probe (PSP) mission. Observations of coherent
electromagnetic waves at ion scales suggests that linear cyclotron resonance
and non-linear processes are dynamically relevant in the inner heliosphere. A
wavelet-based statistical study of coherent waves in the first perihelion
encounter of PSP demonstrates the presence of transverse electromagnetic waves
at ion resonant scales which are observed in 30-50% of radial field intervals.
Average wave amplitudes of approximately 4 nT are measured, while the mean
duration of wave events is of order 20 seconds; however long duration wave
events can exist without interruption on hour-long timescales. Though ion scale
waves are preferentially observed during intervals with a radial mean magnetic
field, we show that measurement constraints, associated with single spacecraft
sampling of quasi-parallel waves superposed with anisotropic turbulence, render
the measured quasi-parallel ion-wave spectrum unobservable when the mean
magnetic field is oblique to the solar wind flow; these results imply that the
occurrence of coherent ion-scale waves is not limited to a radial field
configuration. The lack of strong radial scaling of characteristic wave
amplitudes and duration suggests that the waves are generated {em{in-situ}}
through plasma instabilities. Additionally, observations of proton distribution
functions indicate that temperature anisotropy may drive the observed ion-scale
waves.

Understanding the physical processes in the solar wind and corona which
actively contribute to heating, acceleration, and dissipation is a primary
objective of NASA’s Parker Solar Probe (PSP) mission. Observations of coherent
electromagnetic waves at ion scales suggests that linear cyclotron resonance
and non-linear processes are dynamically relevant in the inner heliosphere. A
wavelet-based statistical study of coherent waves in the first perihelion
encounter of PSP demonstrates the presence of transverse electromagnetic waves
at ion resonant scales which are observed in 30-50% of radial field intervals.
Average wave amplitudes of approximately 4 nT are measured, while the mean
duration of wave events is of order 20 seconds; however long duration wave
events can exist without interruption on hour-long timescales. Though ion scale
waves are preferentially observed during intervals with a radial mean magnetic
field, we show that measurement constraints, associated with single spacecraft
sampling of quasi-parallel waves superposed with anisotropic turbulence, render
the measured quasi-parallel ion-wave spectrum unobservable when the mean
magnetic field is oblique to the solar wind flow; these results imply that the
occurrence of coherent ion-scale waves is not limited to a radial field
configuration. The lack of strong radial scaling of characteristic wave
amplitudes and duration suggests that the waves are generated {em{in-situ}}
through plasma instabilities. Additionally, observations of proton distribution
functions indicate that temperature anisotropy may drive the observed ion-scale
waves.

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