Coordinated observations of two types of diffuse auroras near magnetic local noon by Magnetospheric Multiscale mission and ground all-sky camera

• 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 He2+ (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.

Subject headings

NATURVETENSKAP  -- Fysik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences (hsv//eng)

Keyword

diffuse aurora

dayside diffuse aurora

cold plasmas

ECH wave

throat aurora

MMS

Publication and Content Type

ref (subject category)

art (subject category)