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Astronomy & Astrophysics manuscript no. (will be inserted by hand later)

Summary: Astronomy & Astrophysics manuscript no.
(will be inserted by hand later)
Transition region explosive events: Do they have a coronal
L. Teriaca 1 , M. S. Madjarska 2 and J. G. Doyle 2
1 Osservatorio Astro sico di Arcetri, 50125 Firenze, Italy,
2 Armagh Observatory, College Hill, Armagh BT61 9DG, N. Ireland
Abstract. EUV explosive events are a prominent class of phenomena characterizing the solar transition region.
Their correct location in the wider frame-work of the outer solar atmosphere can provide important insight on
the nature of the transition region itself and its relationship with the hotter corona and the cooler chromosphere.
In this paper we present new high-cadence SUMER observations of the \quiet" Sun obtained simultaneously in
the mid-transition region N v 1238.8  A line (1:8 10 5 K) and in the coronal Mg x 625  A line (1:1 10 6 K). These
observations are aimed at providing information on the behaviour of the coronal plasma during EUV transition
region explosive events detected in N v 1238.8  A. None of the events observed in N v shows any detectable signature
in the Mg x line pro le or in its integrated intensity. The analysis of 1996 observations obtained simultaneously
in N v 1238.8  A and S ii 1253.8  A (3:5  10 4 K) shows, instead, a weak but clear presence of enhanced wings in
the S ii line pro le during a series of events observed in N v. These results suggest that EUV explosive events are
not directly relevant in heating the corona and are characteristic of structures not obviously connected with the
upper corona. The evidence of a chromospheric response suggests that, contrary to some previous suggestions,
explosive events have a chromospheric origin.


Source: Armagh Observatory


Collections: Physics