DIAGNOSING THE TIME-DEPENDENCE OF ACTIVE REGION CORE HEATING FROM THE EMISSION MEASURE. I. LOW-FREQUENCY NANOFLARES
| dc.citation.firstpage | 53 | en_US |
| dc.citation.journalTitle | The Astrophysical Journal | en_US |
| dc.citation.lastpage | 61 | en_US |
| dc.citation.volumeNumber | 758 | en_US |
| dc.contributor.author | Bradshaw, S.J. | en_US |
| dc.contributor.author | Klimchuk, J.A. | en_US |
| dc.contributor.author | Reep, J.W. | en_US |
| dc.date.accessioned | 2013-03-13T19:33:13Z | |
| dc.date.available | 2014-03-19T05:10:03Z | |
| dc.date.issued | 2012 | en_US |
| dc.description.abstract | Observational measurements of active region emission measures contain clues to the time dependence of the underlying heating mechanism. A strongly nonlinear scaling of the emission measure with temperature indicates a large amount of hot plasma relative to warm plasma. A weakly nonlinear (or linear) scaling of the emission measure indicates a relatively large amount of warm plasma, suggesting that the hot active region plasma is allowed to cool and so the heating is impulsive with a long repeat time. This case is called low-frequency nanoflare heating, and we investigate its feasibility as an active region heating scenario here.We explore a parameter space of heating and coronal loop properties with a hydrodynamic model. For each model run, we calculate the slope α of the emission measure distribution EM(T ) ∝ T α. Our conclusions are: (1) low-frequency nanoflare heating is consistent with about 36% of observed active region cores when uncertainties in the atomic data are not accounted for; (2) proper consideration of uncertainties yields a range in which as many as 77% of observed active regions are consistent with low-frequency nanoflare heating and as few as zero; (3) low-frequency nanoflare heating cannot explain observed slopes greater than 3; (4) the upper limit to the volumetric energy release is in the region of 50 erg cm−3 to avoid unphysical magnetic field strengths; (5) the heating timescale may be short for loops of total length less than 40Mm to be consistent with the observed range of slopes; (6) predicted slopes are consistently steeper for longer loops. | en_US |
| dc.embargo.terms | 1 year | en_US |
| dc.identifier.citation | Bradshaw, S.J., Klimchuk, J.A. and Reep, J.W.. "DIAGNOSING THE TIME-DEPENDENCE OF ACTIVE REGION CORE HEATING FROM THE EMISSION MEASURE. I. LOW-FREQUENCY NANOFLARES." <i>The Astrophysical Journal,</i> 758, (2012) The American Astronomical Society: 53-61. http://dx.doi.org/10.1088/0004-637X/758/1/53. | |
| dc.identifier.doi | http://dx.doi.org/10.1088/0004-637X/758/1/53 | en_US |
| dc.identifier.uri | https://hdl.handle.net/1911/70571 | |
| dc.language.iso | eng | en_US |
| dc.publisher | The American Astronomical Society | |
| dc.rights | Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use. | |
| dc.subject.keyword | sun | en_US |
| dc.subject.keyword | corona | en_US |
| dc.title | DIAGNOSING THE TIME-DEPENDENCE OF ACTIVE REGION CORE HEATING FROM THE EMISSION MEASURE. I. LOW-FREQUENCY NANOFLARES | en_US |
| dc.type | Journal article | en_US |
| dc.type.dcmi | Text | en_US |
| dc.type.publication | publisher version | en_US |