Intriguing Observations of a Failed Eruption?

We present observations of a (partially) failed eruption of a magnetic flux rope following an M9.3 flare on 24 October 2013 around 00:05.

Figure 1. shows a PROBA2 SWAP 171Å image of the source active region (AR A), where the initial flare was observed. The flare was accompanied by a destabilization of the surrounding field and intriguing flows.

During the initial stages of the eruption multi-thermal material trapped on the erupting field was observed to rise before abruptly changing direction and flowing to the adjacent AR (B).

There was no clear accompanying CME signature observed in SOHO LASCO C2 observations.

The flare produced irradiances over 5 W m-2 in the Zirconium channel (6-20 nm + a contribution <2 nm) of the PROBA2 LYRA Radiometer (see Figure 2).

West, M.J.1, Zuccarello, F.2,3, Seaton, D.1, Rachmeler, L.1 , Ryan, D1, Mierla, M1 and Vansintjan, R1 1Royal Observatory of Belgium (Belgium) 2Leuven (Belgium) 3Obs. Paris-Meudon (France)

In Figure 3 material is seen to emerge from AR (A) around 00:20 UT before abruptly changing direction around 00:50 UT, and flowing towards AR (B). The final flow speeds are ~271±42 km s-1.

We constructed a field line extrapolation of the surrounding field around the time of the eruption, based on the methods described in Alissandrakis (1981), also see Zuccarello (2011).

The reconstructed topology is shown in Figure 4. The two ARs are highlighted by the red bipolar field lines. The overlying fields are connected to a null point located between the ARs.

The material erupting from AR (A) may interact with the overlying (brown) field lines, which are restructured through a series of magnetic reconnections. The material then follows the new topology to footpoints B and C indicated in Figure 4 (ii). The material flowing towards the footpoints can be seen in Figures 3 (iv) and (v).

A brief analysis of RHESSI data (See Figure 5) reveals several peaks in the 3 - 6 and 6-12 keV bandpass observations. These peaks correlate with brightenings observed around the time of the change in direction of the erupting material. This may be evidence of the field lines restructuring and reconnecting. Further analysis is required.

Figure 6. shows the post eruption corona and transition region in multiple bandpasses of AIA, showing that the erupting material had a broad temperature and energy range.

Figure 2. PROBA2 LYRA aluminum (blue) and zirconium (black) irradiance curves showing the magnitude of the associated M9.3 flare.

Figure 6. SDO AIA images. (i) 170Å – 5×103 K; (ii) 304Å – 5×104 K; (iii) 160Å – 5×103 K - 1×105 K; (iv) 171Å – 6.3×105 K; (v) 193Å – 1.2×106 K; (vi) 211Å – 2×106 K; (vii) 335Å – 2.5×106 K; (viii) 94Å – 6.3×106 K; (ix) 131Å – 4.0×105 - 1.6×107 K and (x) HMI magnetogram at ~21-Oct-2013 30:00. The erupting material can be seen emerging from AR (A) in all EUV band passes.

Figure 1. PROBA2 SWAP Image of the failed eruption of 24 Oct 2013. The flare occurred in AR (A). The eruption flows started in AR (A), and later connected to AR (B). The grey inset shows a running difference image.

(A)

(B)

00:06 UT - Flare occurs around 00:05 UT in AR (A). AR becomes active with several down-flows observed.

00:26 UT - The eruption emerges from AR (A). Connections with AR (B) already seen.

00:34 UT - The eruption slows and the eruptive material begins to change direction.

01:13 UT - The eruptive material is abruptly changes direction. This may be due to new magnetic connectivities with overlying fields.

01:22 - The majority of the emerging material changes direction and flows to AR (B). Some material flows back to AR (A).

01:33 UT - the last of the material flows to AR (B).

01:48 - Both ARs slowly return to pre eruptive states.

Figure 3. A sequence of SWAP running difference Images showing the various stages of the failed eruption.

(A)

(B)

i ii iii iv v vi vii

Figure 4. Magnetic field extrapolation based on the methods described in Alissandrakis (1981). Field lines from different magnetic domains are highlighted with different colors.

(A)

(B)

i ii

iii iv

C

B

Figure 5. Summary count rates from RHESSI. Several peaks in the 3-6 and 6-12 keV bandpass correlate with brightenings observed when the erupting material changes direction.

This research is on-going work, we continue to investigate this intriguing failed eruption in various observations and models. The pair of ARs were dynamic throughout their lifetimes producing multiple eruptions and flows. The unanswered question as to why this eruption failed remains to be discovered.

i ii iii iv

vi vii viii ix

v

x