Coordinated observations of two types of diffuse auroras near magnetic local noon by Magnetospheric Multiscale mission and ground all‐sky camera. Issue 16 (19th August 2017)

• Record Type: Journal Article
• Authors: Han, D.‐S.; Li, J.‐X.; Nishimura, Y.; Lyons, L. R.; Bortnik, J.; Zhou, M.; Liu, J.‐J.; Hu, Z.‐J.; Hu, H.‐Q.; Yang, H.‐G.; Fuselier, S. A.; Le Contel, O.; Ergun, R. E.; Malaspina, D.; Lindqvist, P.‐A.; Pollock, C. J.
• Is Part Of: Geophysical research letters. Volume 44:Issue 16(2017)
• Page Start: 8130
• Page End: 8139
• Publication Date: 2017-08-19
• Subjects: diffuse aurora -- dayside diffuse aurora -- cold plasmas -- ECH wave -- throat aurora -- MMS; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1002/2017GL074447
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: Structured diffuse auroras are often observed near magnetic local noon (MLN), but their generation mechanisms are poorly understood. We have found that two types of structured diffuse auroras with obviously different dynamical properties often coexist near MLN. One type usually drifts from low to high latitude with higher speed and shows pulsation. The other type is always adjacent to the discrete aurora oval and drifts together with nearby discrete aurora with much lower speed. Using coordinated observations from MMS and ground all‐sky imagers, we found that the two types of diffuse auroras are well correlated with number density increase of O + (from the ionosphere) and of He 2+ (from magnetosheath) ions, respectively. These observations indicate that mangetosheath particles penetrated into the magnetosphere also can play an important role for producing the dayside diffuse aurora. In addition, for the first time, electron cyclotron harmonic waves are observed associated with dayside diffuse aurora. Key Points: Two types of structured diffuse auroras observed near magnetic local noon with obviously different dynamical properties are identified Types 1 and 2 are associated with number density increase of O + from the magnetosphere and of He 2+ from the magnetosheath, respectively For the first time, ECH waves, but no whistler mode chorus waves, were observed associated with dayside diffuse auroras