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MAGNETIC FIELD STRENGTH IN THE UPPER SOLAR CORONA USING WHITE-LIGHT SHOCK STRUCTURES SURROUNDING CORONAL MASS EJECTIONS
| Content Provider | Scilit |
|---|---|
| Author | Kim, R. -S. Gopalswamy, Nat Moon, Y. -J. Cho, K. -S. Yashiro, Seiji |
| Copyright Year | 2012 |
| Description | Journal: The Astrophysical Journal To measure the magnetic field strength in the solar corona, we examined 10 fast (≥1000 km $s^{–1}$) limb coronal mass ejections(CMEs) that show clear shock structures in Solar and Heliospheric Observatory/Large Angle and Spectrometric Coronagraph images. By applying the piston-shock relationship to the observed CME's standoff distance and electron density compression ratio, we estimated the Mach number, Alfvén speed, and magnetic field strength in the height range 3-15 solar radii $(R_{s}$ ). The main results from this study are as follows: (1) the standoff distance observed in the solar corona is consistent with those from a magnetohydrodynamic model and near-Earth observations; (2) the Mach number as a shock strength is in the range 1.49-3.43 from the standoff distance ratio, but when we use the density compression ratio, the Mach number is in the range 1.47-1.90, implying that the measured density compression ratio is likely to be underestimated owing to observational limits; (3) the Alfvén speed ranges from 259 to 982 km $s^{–1}$ and the magnetic field strength is in the range 6-105 mG when the standoff distance is used; (4) if we multiply the density compression ratio by a factor of two, the Alfvén speeds and the magnetic field strengths are consistent in both methods; and (5) the magnetic field strengths derived from the shock parameters are similar to those of empirical models and previous estimates. |
| Related Links | http://iopscience.iop.org/article/10.1088/0004-637X/746/2/118/pdf |
| ISSN | 0004637X |
| DOI | 10.1088/0004-637x/746/2/118 |
| Journal | The Astrophysical Journal |
| Issue Number | 2 |
| Volume Number | 746 |
| Language | English |
| Publisher | IOP Publishing |
| Publisher Date | 2012-02-20 |
| Access Restriction | Open |
| Subject Keyword | Journal: The Astrophysical Journal Astronomy and Astrophysics Coronal Mass Ejection Magnetohydrodynamics Earth Observation Compression Ratio |
| Content Type | Text |
| Resource Type | Article |
| Subject | Astronomy and Astrophysics Space and Planetary Science |
