Conjugate ground-spacecraft observations of VLF chorus elements

0497713 - ÚFA 2019 BE eng A - Abstrakt
Demekhov, A. G. - Manninen, J. - Santolík, Ondřej - Titova, E. E.
Conjugate ground-spacecraft observations of VLF chorus elements.
2 nd URSI AT-RASC Proceedings. Gent: URSI, 2018.
[URSI Atlantic Radio Science Meeting (AT-RASC) /2./. 28.05.2018-01.06.2018, Gran Canaria]
Institucionální podpora: RVO:68378289
Klíčová slova: magnetosphere * VLF hiss emissions * chorus emissions * Van Allen Probes spacecraft * EMFISIS
Obor OECD: Fluids and plasma physics (including surface physics)
http://www.ursi.org/proceedings/procAT18/papers/chorusconj.pdf

We present the results of simultaneous observations [1] of VLF chorus elements at the ground-based station Kannuslehto in Northern Finland and on board Van Allen Probe A. Visual inspection and correlation analysis of the data reveal one-to-one correspondence of several (at least 12) chorus elements following each other in a seq uence. Poynting flux calculated from electromagnetic fields measured by the Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) instrument on board Van Allen Probe A shows that the waves propagated at small angles to the geomagnetic field and oppositely to its direction, that is, from northern to southern geographic hemisphere. The spacecraft was located at L ' 4.1 at a geomagnetic latitude of −12.4 degrees close to the plasmapause and inside a localized density inhomogeneity with about 30% density increase and a transverse size of about 600 km.
The observed waves are part of a long-lasting (about two hours) wave event including both chorus and hiss-like
emissions.
The time delay between the waves detected on the ground and on the spacecraft is about 1.3 s, with ground-based detection leading spacecraft detection. The measured time delay is consistent with the wave travel time of quasiparallel whistler-mode waves for a realistic profile of the plasma density distribution along the field line. Therefore, chorus wave packets were detected first at Kannuslehto on the ground, and then in 1.3 to 1.4 s they reached the Van Allen Probe A on the opposite side of the magnetic equator.
The results suggest that chorus discrete elements can preserve their spectral shape during a hop from the generation region to the ground followed by reflection from the ionosphere and return to the near-equatorial region.

Trvalý link: http://hdl.handle.net/11104/0290222