Examining EUV Brightenings and Their Effects

EUV Brightenings, often called 'campfires', are small but significant events that happen in the quiet areas of the Sun. Even though they seem frequent, many questions still remain about them, especially around their temperatures and how they behave.

In this exploration, we look to see if any responses can be spotted in the Transition Region when these small brightenings occur. We also want to find out if the signals we observe match up with other known events in the transition region, like Explosive Events (EEs).

EUV brightenings have been noticed in data collected by the Solar Orbiter's Extreme Ultraviolet Imager (EUI). By using a detection method, we were able to spot these brightenings in data collected on a particular day in March. We also analyzed images and spectra collected by the Interface Region Imaging Spectrograph (IRIS) to check if any transition region responses were present.

From our observations, we can see that EUV brightenings show different responses in the IRIS data. Some events had clear signs in the specific filters we used, while others did not show any response. In some cases, the intensity of the EUV signals peaked before, during, or after the signals from IRIS. This suggests that the cause of these brightenings might not be consistent; some could be influenced by Magnetic Activity, while others might not.

EUV brightenings are used to describe a variety of small events in the Sun’s atmosphere. The reasons behind these brightenings might differ, and conducting more studies is necessary to discover their role in larger solar events, such as the heating of the corona.

#The Background of EUV Brightenings

Small-scale brightenings have been observed throughout the solar atmosphere, from the surface to the outer layers. This phenomenon has been studied for over a hundred years, first being recognized in a specific form, now called Ellerman bombs (EBs). Since that time, many other types of brightenings have been reported, each with distinct properties.

The launch of new satellites like IRIS and Solar Orbiter has provided fresh insights into these brightenings. Recent observations have clarified our knowledge regarding events like IRIS bursts and EUV brightenings, enhancing our grasp of how energy is released in the upper solar atmosphere. Observations from both satellites have allowed scientists to connect brightenings observed in different temperature ranges, shedding light on the physical processes behind these events and how they relate to coronal heating.

Solar Orbiter’s EUI has detected thousands of small EUV brightenings in quiet Sun images. These brightenings occur at very small spatial scales, even below what previous satellite data could capture. Despite their recent discovery, these events have been thoroughly studied through both observations and simulations. For instance, combining data from the Solar Dynamics Observatory (SDO) with data from Solar Orbiter has enabled scientists to view these events from different angles and gather more information about their locations within the Sun's atmosphere.

#The Purpose of This Study

One area that has not been fully explored is whether EUV brightenings show signs in different temperature parts of the solar atmosphere. Past studies have found cool plasma near some EUV brightenings, but it is still uncertain if all brightenings respond in the transition region. If these brightenings are caused by magnetic reconnection, it is very likely that they could show signs of other bursts happening at the same time in the solar atmosphere.

In this study, we aim to advance our knowledge of EUV brightenings by examining data collected during coordinated observations of Solar Orbiter and IRIS. We want to see if there are signs of these brightenings in transition region temperatures and whether these signals match those of other known bursts.

We will begin by introducing the data analyzed in this article. Following that, we will present the results of our analysis, followed by a brief discussion before concluding.

#Data Collection and Analysis

Our study examines a quiet-Sun area captured by the EUI using a specific filter. The observations were made between specified times in March. During this period, Earth was positioned such that coordination with ground-based instruments was possible.

The images captured were extensive, with high resolution, giving detailed insights into the solar surface. The dataset had a specific cadence, allowing for decent time resolution of the observed events. By downloading and processing this level-2 data, the identification of EUV brightenings was made possible through an automated algorithm. This algorithm facilitated the conversion of raw data into a more manageable format while maintaining spatial details.

We found several regions within the area studied that exhibited EUV brightening activity. Each region provided sufficient evidence for comparing the features with observations from IRIS.

#Extended EUV Brightenings

We began by examining whether any signs could be detected in the transition region related to elongated EUV brightenings. We identified several events, which were detected over a few minutes. During our analysis, we plotted the intensity of the EUV brightening over time, showing clear outlines of the brightenings.

In one instance, an extended EUV brightening was observed, with corresponding IRIS responses seen in the SiIV filter, especially after the EUV brightening had occurred. Although the MgII filter did not show any significant response, the SiIV filter provided intriguing insights into the behavior of the extended structure.

For other events, a similar pattern emerged where the intensity was observed to peak in specific time frames. This indicates a possible sequence of energy changes or heating events occurring in the solar atmosphere.

#Lightcurves and Intensity Patterns

To analyze the intensity changes over time associated with EUV brightenings, we created lightcurves that summarized changes in brightness within the observed regions. These lightcurves revealed interesting patterns, including scenarios where the IRIS signals peaked before, during, or even after the EUV brightening activities.

In some instances, the SiIV responses showed noticeable intensity increases in correlation with the EUV brightening. However, for others, the timing varied, suggesting a more complex interaction taking place.

#Complex EUV Brightenings

In addition to the extended brightenings, we also identified more complex behavior in some EUV brightenings. These involved multiple small brightenings that showed rapid changes in intensity and structure. Detailed observations revealed patterns of brightening that suggested a series of energy releases occurring in quick succession.

Lightcurves from these complex events indicated varying behaviors, with some peaks appearing during the decay phases of EUV brightening. This complexity hints at intricate processes happening within the solar atmosphere during these events.

#EUV Brightenings Without IRIS Responses

Despite the connections identified between some EUV brightenings and IRIS responses, there were instances where no clear responses could be observed. In certain regions, we identified EUV brightenings that appeared substantial but did not produce any detectable signs in the IRIS data.

These cases raise interesting questions about whether some brightenings occur in layers of the solar atmosphere that are too hot for the IRIS filters to capture effectively. It might mean that the plasma has already reached temperatures above what the IRIS instruments can detect by the time the EUV brightening occurs.

#Summary of Findings

In summarizing our findings, it is evident that there is no uniform response to EUV brightenings as observed by IRIS. While some brightenings displayed clear connections to both MgII and SiIV data, others lacked any detectable response.

Our analysis of lightcurves indicated varying patterns of intensity increases, suggesting that these observations might point to either current heating events or locations where plasma has cooled. The complexity of these findings illustrates the diverse nature of EUV brightenings and their potential links to various solar phenomena.

This study highlights the importance of continued observations and analysis of EUV brightenings to better understand their role in solar dynamics and their implications for understanding the Sun's atmosphere as a whole. Future work should focus on expanding the dataset and refining the analysis techniques to uncover more about these fascinating solar events.