Research On The Distribution Of Magnetosonic Waves In The Inner Magnetosphere And Its Interaction With Ring Current Protons

Due to the high ionization and the existence of the earth's intrinsic magnetic field in the inner magnetosphere,a large number of charged particles are trapped around the earth,forming the ionosphere,ring current and radiation belts.The inner magnetosphere have always been the focus of research by space physicists in recent years due to their active particles states and various oscillations.In the inner magnetosphere,magnetosonic(MS)waves have a wide distribution and occur frequently,so MS waves have attracted more and more attention.Based on the observations of the Van Allen Probes,this paper conducts a statistical analysis of the various characteristics of MS waves in the radiation belts.We have launched scientific exploration and analysis in the automatic identification of magnetosonic waves and the establishment of amplitude and distribution models.In addition,we use the quasi-linear diffusion theory,conbined with the conjugation observations,to study the effects of magnetosonic waves on the ring current protons.The main conclusions of this paper are as follows:1.Completed an automatic detection algorithm of MS wave based on VAPThe two-year observation data of Van Allen Probe-A(VAP-A)from September 16,2012 to September 30,2014 are calculated.Through statistical analysis of the polarization,wave normal angle and planarity of various inner magnetospheric plasma waves,there is a significant difference between the statistical distributions of the main characteristics of the MS waves and other waves.After eliminating the background noise and the near-ground noise at L<1.8,we have established an automatic detection algorithm for MS waves,that is,the absolute value of the wave polarization is less than0.2,the wave normal angle is greater than 70°,and the frequency range is 2 Hz to 1.5f _LHR(the lower hybrid resonance frequency).Finally,we checked the planarity of the MS waves obtained through these criteria and tested the automatic identification algorithm on the data of the Van Allen probe,to verify the reliability of the method.In addition,using the distribution results of our automatic algorithm,we found that in the plasmapause,as the magnetic latitude increases,it is easier to excite MS waves on the equatorial side,and extend higher latitude.2.Constructed the MS waves amplitude model based on VAPBased on the observations of Van Allen Probe-A from September 19,2012 to February 28,2016,we respectively show the relationships between the MS waves amplitude B_w and kp index,and wave normal angle(WNA),and normalized frequency(nor F),and spatial location.Then,we established an analytical regression model of MS waves amplitude based on geomagnetic activity(represented by kp index),L-value(L),magnetic local time(MLT),magnetic latitude(?)and MS waves characteristic parameters(WNA and nor F)as inputs.From the B_w model,we found that the MS waves amplitude B_w is positively correlated with the intensity of geomagnetic activity both inside and outside the plasmapause.With the increase of kp index,B_w in the plasmapause can reach higher value than outside the plasmapause.The B_w distribution on the normalized frequency shows that most of the wave energy is concentrated in the lower harmonics,resulting from the excitation mechanism of the MS wave.In addition,the B_w distribution on the wave normal angle indicates that the wave with a larger wave normal angle has a higher amplitude.Our analytical MS wave model is in good agreement with global distribution of the observed in the 3-D space composed of L,MLT and?,and its fitting accuracy coefficient R² is above 0.9.3.Completed the statistical analysis and corresponding models of MS waves at WNA and nor FBased on the observations of Van Allen Probe-A,an automatic detection algorithm is used to obtain a large number of MS waves,and their distributions on the nor F and WNA are presented.From the distribution of the WNA of the MS waves,it can be known that the MS waves are concentrated at a WNA of?86°,whether inside or outside the plasmapause.In addition,through the nor F distribution of the MS waves,the MS waves outside the plasmapause are concentrated in the local proton cyclotron harmonics of 1-10,which explains most of MS waves outside the plasmaapuse are generated by local excitation,but there is no such situation inside plasmapause but only concentrated at a low nor F.It demonstrates that the MS waves inside the plasmapasuse are propagated elsewhere.4.Based on the magnetospheric and ionospheric conjugation observations,discovered the ionospheric characteristics of ring current protons scattered by MS wavesIn the plasmasphere,Van Allen probe observed MS waves on-site.At the height of the ionosphere in sub-auroral zone,the NOAA 16 satellite simultaneously observed a significant increase in the flux of mirroring protons,but there was no significant change in the flux of ring current protons that had precipitated.The theoretical calculation of the pitch-angle diffusion coefficients of the ring current protons confirms that the observed MS wave can only lead to flux enhancement,and is only used for the mirroring protons,and cannot precipitate the ring current protons,which is consistent with the observation results of NOAA 16.Our results have revealed the ionospheric signatures of ring current protons scattered by MS waves in the inner magnetosphere.