%0 Journal Article %1 LiTypeIII %A Li, B. %A Cairns, Iver H. %A Yan, Y. H. %A Robinson, P. A. %D 2011 %J The Astrophysical Journal Letters %K III Type burst plasma radio %N 1 %P L9 %T Decimetric Type III Bursts: Generation and Propagation %U http://stacks.iop.org/2041-8205/738/i=1/a=L9 %V 738 %X Simulations are presented for decimetric type III radio bursts at 2 f p , where f p is the local electron plasma frequency. The simulations show that 2 f p radiation can be observed at Earth in two scenarios for the radiation's generation and propagation. In Scenario A, radiation is produced and propagates in warm plasmas in the lower corona that are caused by previous magnetic reconnection outflows and/or chromospheric evaporation. In Scenario B radiation is generated in normal plasmas, then due to its natural directivity pattern and refraction, radiation partly propagates into nearby regions, which are hot because of previous reconnection/evaporation. The profiles of plasma density n e ( r ) and electron temperature T e ( r ) in the lower corona ( r – R ☉ ##IMG## http://ej.iop.org/icons/Entities/lsim.gif lsim 100 Mm) are found to be crucial to whether radiation can be produced and escape at observable levels against the effects of free-free absorption, where r is the heliocentric distance. Significantly, the observed wide ranges of radiation properties (e.g., drift rates) require n e ( r ) with a large range of scale heights h s , consistent nonetheless for Scenario B with short observed EUV loops. This is relevant to problems with large h s inferred from tall EUV loops. The simulations suggest: (1) n e ( r ) with small h s , such as n e ( r ) ##IMG## http://ej.iop.org/icons/Entities/vprop.gif vprop ( r – R ☉ ) –2.38 for flaring regions, are unexpectedly common deep in the corona. This result is consistent with recent work on n e ( r ) for r ##IMG## http://ej.iop.org/icons/Entities/ap.gif ≈ (1.05-2) R ☉ extracted from observed metric type IIIs. (2) The dominance of reverse-slope bursts over normal bursts sometimes observed may originate from asymmetric reconnection/acceleration, which favors downgoing beams.

@article{LiTypeIII, abstract = {Simulations are presented for decimetric type III radio bursts at 2 f p , where f p is the local electron plasma frequency. The simulations show that 2 f p radiation can be observed at Earth in two scenarios for the radiation's generation and propagation. In Scenario A, radiation is produced and propagates in warm plasmas in the lower corona that are caused by previous magnetic reconnection outflows and/or chromospheric evaporation. In Scenario B radiation is generated in normal plasmas, then due to its natural directivity pattern and refraction, radiation partly propagates into nearby regions, which are hot because of previous reconnection/evaporation. The profiles of plasma density n e ( r ) and electron temperature T e ( r ) in the lower corona ( r – R ☉ ##IMG## [http://ej.iop.org/icons/Entities/lsim.gif] {lsim} 100 Mm) are found to be crucial to whether radiation can be produced and escape at observable levels against the effects of free-free absorption, where r is the heliocentric distance. Significantly, the observed wide ranges of radiation properties (e.g., drift rates) require n e ( r ) with a large range of scale heights h s , consistent nonetheless for Scenario B with short observed EUV loops. This is relevant to problems with large h s inferred from tall EUV loops. The simulations suggest: (1) n e ( r ) with small h s , such as n e ( r ) ##IMG## [http://ej.iop.org/icons/Entities/vprop.gif] {vprop} ( r – R ☉ ) –2.38 for flaring regions, are unexpectedly common deep in the corona. This result is consistent with recent work on n e ( r ) for r ##IMG## [http://ej.iop.org/icons/Entities/ap.gif] {≈} (1.05-2) R ☉ extracted from observed metric type IIIs. (2) The dominance of reverse-slope bursts over normal bursts sometimes observed may originate from asymmetric reconnection/acceleration, which favors downgoing beams.}, added-at = {2012-02-07T10:58:34.000+0100}, author = {Li, B. and Cairns, Iver H. and Yan, Y. H. and Robinson, P. A.}, biburl = {https://www.bibsonomy.org/bibtex/2b9bfbb4828a3fd99e90e2121f1056694/ursg}, description = {Decimetric Type III Bursts: Generation and Propagation}, interhash = {5f198864798dbf8eab3b6c8e8bbd1643}, intrahash = {b9bfbb4828a3fd99e90e2121f1056694}, journal = {The Astrophysical Journal Letters}, keywords = {III Type burst plasma radio}, number = 1, pages = {L9}, timestamp = {2012-02-07T10:58:34.000+0100}, title = {Decimetric Type III Bursts: Generation and Propagation}, url = {http://stacks.iop.org/2041-8205/738/i=1/a=L9}, volume = 738, year = 2011 }