The IAU Solar Target Identifier - A Good Thing

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Number: 243
1st Author: Hugh Hudson
2nd Author: John Leibacher
Published: December 29, 2014
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Naming conventions have always been a nuisance in astronomy. Who among us can readily identify Messier 1 with Tau XR-1, for example, or list even half a dozen of the 37 other names it has in the SIMBAD service? Solar identifications are worse than in other fields of astronomy because the interesting items are always transient and need a time reference.

Noting this, members of the solar-physics community established a naming convention for solar targets in 2010; this was adopted by Solar Physics (Ref. [1)] They have also taken the necessary steps to have this convention recognized by the International Astronomical Union IAU. These articles describe the potential utility of having a uniform nomenclature, which in its abbreviated form uniquely defines a flare by its time only: SOL2011-02-15T01:56 almost uniquely identifies the first X-class flare of Cycle 24, which we will use as an example below. Note the merit of this system: it locks the community down to a searchable time of occurrence; please read Ref. [1] for more of the bells and whistles that can extend the metadata embodied in the identifier. Here we have taken advantage of the time field T01:56 to give the standard GOES peak time for the event, and have omitted the location fields.

For aficionados of time styles, the SOL identifier complies with the ISO 8601 and CCSDS standards, and can easily merge into SolarSoft IDL. Karel Schrijver notes that the identifier already works in full detail in the Heliophysics Events Knowledgebase; see this recent example.


In this Nugget we describe how we have used this capability; the RHESSI team picked up on this immediately with the publication of the RHESSI monograph in 2011 (Ref. 2). This reference contains links to the individual chapters and to the index, which features the IAU target identifiers. The listing conveniently shows 116 individual solar flare events (one from the 1800s, 40 from the 1900s, and 75 from the 2000s). That in itself is a bit interesting, since the non-RHESSI events thus amounted to something like 1/3 of the flares actually discussed in this RHESSI-oriented book.

How well has the community taken up this notation? One commonly sees it now in new papers, and one can search for individual events or groups of events via the wonderful NASA ADS bibliographic service. We have done this for some test cases, as illustrated in Figure 1. This shows all of the entries with SOL2002, ie for flares of that year all of the entries with SOL2011, ditto, and specifically SOL2011-02-15, our demonstration event.

Figure 1: The community takeup as found by using the ADS "fulltext" search capability, for two memorable years and for one specific flare. The counts show the number of articles mentioning the chosen target. The individual peak for the 2002 listing would be for SOL2002-07-23, RHESSI's first gamma-ray event. By year, one can note the steady annual increases as more and more papers adopt the system - SOL2011-02-15 has not peaked yet!


Without being systematic about the many virtues of a uniform target identifier, for which see Ref. 1, the uses we have put this to in RHESSI work are already extensive and helpful. Different authors, for example those of the different chapters of the RHESSI monograph (Ref. 2) can quickly relate their interest in a specific flare event with properties found by somebody else. At some point in the future we hope that this convenience will become almost universal.

One could almost begin to think about an "event review" of SOL2011-02-15, based on the 19 articles thus identified; in our community we often become very enthusiastic about a single event, but seldom try to synthesize the data into a critical review. It is too bad that this scheme will not work for more influential older events such as SOL1859-09-01 or SOL1992-01-13.


[1] "Solar Observation Target Identification Convention for Solar Physics"

[2] "High-Energy Aspects of Solar Flares"

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