Open AccessBulk flow velocities in the solar corona
Author(s) -
Lewis D. J.,
Simnett G. M.
Publication year - 2000
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.2000.03759.x
Subject(s) - physics , coronal mass ejection , coronagraph , corona (planetary geology) , astrophysics , coronal hole , acceleration , solar wind , observatory , solar observatory , astronomy , solar minimum , solar radius , interplanetary medium , spacecraft , solar prominence , solar cycle , plasma , magnetic field , interplanetary spaceflight , planet , classical mechanics , astrobiology , venus , exoplanet , quantum mechanics
We present velocity estimates of bulk motions in the solar corona using data from the Large Angle Spectrometric Coronagraph (LASCO) aboard the Solar and Heliospheric Observatory spacecraft ( SOHO ). We describe a new technique which automatically provides a mass‐weighted mean velocity profile in an entirely objective fashion without the need for individual event identification. A weighted velocity profile of this kind reflects the motion of the energetically dominant component of the coronal mass ejection (CME) mass spectrum and is of particular interest in consideration of the overall energy budget of the CME process. We consider the mean motion within three latitudinal bands centred at 0°, 20° and 40° over a one‐year period around the time of solar minimum. We find terminal velocities within the LASCO field of around 300 km s −1 in all latitude bands but note a latitudinal dependence in CME evolution through the low corona prior to reaching these velocities. We find evidence that ejections in the equatorial zone undergo continuous acceleration whilst at higher latitudes a discrete burst of acceleration is seen to occur at around 4 R ⊙ from the Sun's centre with relatively little acceleration thereafter. We also consider the energy deposition rates necessary to generate these profiles.