[IGPP Everyone] Space Physics seminar - Fri. Jan. 14, 03:30 PM PST - Magnetic Switchbacks in the Young Solar Wind with Parker Solar Probe (O. Agapitov, UCB SSL)

[Emmanuel V. Masongsong]

SPACE PHYSICS SEMINAR 



DEPARTMENT OF EARTH, PLANETARY, AND SPACE SCIENCES 

DEPARTMENT OF ATMOSPHERIC AND OCEANIC SCIENCES 
UNIVERSITY OF CALIFORNIA, LOS ANGELES 

ZOOM LINK PROVIDED BELOW 


https://ucla.zoom.us/j/98070654630?pwd=aWdrSktueG9xWjU3cDZiQUhGRXV0UT09 



Magnetic Switchbacks in the Young Solar Wind: Parker Solar Probe observations 

Oleksiy Agapitov 

UC Berkeley Space Sciences Lab 

(with James F. Drake, Marc Swisdak, and the PSP team) 



A major discovery of Parker Solar Probe (PSP) was the presence of large numbers of localized increases in the radial solar wind speed and associated sharp deflections of the magnetic field - switchbacks (SB). A possible generation mechanism of SBs is through magnetic reconnection between open and closed magnetic flux near the solar surface termed interchange reconnection that leads to the ejection of flux ropes (FR) into the solar wind. The role of FRs merging in controlling the structure of SB in the solar wind is explored through direct observations, analytic analysis, and numerical simulations. Observations also suggest that SBs undergo merging, which is shown to be energetically favorable to reduce the strength of the wrapping magnetic field and that this drives the observed elongation of SBs. A further consequence is a resulting dominance of the axial magnetic field within SBs that leads to the characteristic sharp rotation of the magnetic field into the axial direction at the SB boundary that is revealed in observations. Observations by PSP reveal the existence of intensive plasma wave bursts with frequencies below 0.1 fce (from tens of Hz to 150 Hz in the spacecraft frame) collocated with the switchbacks boundaries. Sunward propagation with depletion of magnetic field magnitude leads to a significant Doppler frequency downshift of whistler waves from 200-300 Hz (0.2-0.5 fce) down to 20-80 Hz in the spacecraft frame. Their peak amplitudes can be as large as 2 to 4 nT. Such values represent approximately 10-20% of the background magnetic field. We have evaluated the properties of these waves collocated with dips of magnetic field related to switchback boundaries, the mechanisms of wave generation: the generation of these waves is supported by the modified electron distribution with increased transverse temperature anisotropy inside the magnetic holes; and the effects on solar wind suprathermal particles from interaction with these waves: sunward propagating whistler waves efficiently interact with the high energy solar wind electrons (in the energy range up to 1 keV) scattering the strahl population of suprathermal electrons into a halo population due to the most efficient cyclotron resonance interaction . 


Friday, January 14, 2022 

3:30 - 5:00 PM 

In-Charge: Vassilis Angelopoulos 






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