The Prediction Panel forecasts the sunspot number expected for solar maximum and has predicted Cycle 25 to reach a maximum of occurring in July, The error bars on this prediction mean the panel expects the cycle maximum could be between with the peak occurring between November and March Please send comments and suggestions to swpc.
Skip to main content. R1 Minor Radio Blackout Impacts. HF Radio: Weak or minor degradation of HF radio communication on sunlit side, occasional loss of radio contact. Navigation: Low-frequency navigation signals degraded for brief intervals. The magnitude of these short-term effects is comparable to those caused by large but much less frequent solar proton events 4 , 5.
As ozone is important to atmospheric heating and cooling rates, this level of ozone variation could significantly affect the local mesospheric temperature balance 6. Our results emphasize the importance of the EEP effect on mesospheric ozone and significantly improve our understanding of the impacts of the energetic particles on the atmosphere.
Solar cycle 23 SC23 was one of the longest cycles since and exhibited large variation in solar UV radiation and geomagnetic activity solar storms, energetic particle precipitation. In , during the declining phase of SC23, the majority of the days were geomagnetically disturbed. In contrast, the deep solar minimum that occurred in showed the lowest activity since the beginning of the Twentieth century. The current solar cycle SC24 is so far the weakest cycle in the last years.
For this period, EEP events were strongest and most frequent during the transition between SC23 maximum and the following minimum Fig. The occurrence of solar proton events SPEs peaked during high solar activity red numbers in Fig. We now consider the 60 major EEP events that occurred between and For these, the satellite measurements show EEP-induced ozone loss occurring consistently in both hemispheres Fig.
The differences between the average responses is partially because of the different vertical resolutions of the observations but is also connected to data availability for some events. For example, the MLS data do not cover the period — that contained multiple extremely strong and long-lasting EEP events.
The response of mesospheric ozone to EEP is immediate; however, the magnitude and duration of the depletion can differ depending on both the characteristics of the event as well as the season Fig. Over the to km altitude range, these events are comparable to the effects of large SPEs. The effect of EEP is typically more pronounced during the wintertime Fig. The event lasted 15 days, with major forcing on 10 of those days and occurred right after Halloween SPE event.
White numbers: O 3 loss at different altitudes. To assess the sensitivity and robustness of our results, we carried out a superposed epoch analysis of the 60 largest EEP events Fig. All SPE periods that could possibly affect the results were excluded from the analysis.
The ozone depletion coincides closely with EEP increases and can last from 3 to 10 days, depending on the EEP duration. A similar superposed epoch analysis for a randomly selected data set Supplementary Fig. The increasing trend in percentage difference in O 3 in the random epoch analysis is caused by a seasonal bias in the observation data sets.
The superposed EEP events shown in Fig. The average ozone loss because of EEP Fig. Although the duration of the forcing for individual EEP events is only a few days, the high frequency of the events during active years Fig. Determining EEP-related ozone anomaly as a function of year or solar cycle is not straight forward because the temporal distribution of EEP events does not smoothly vary across the solar cycle.
For example, the majority of the strong EEP events were observed during the declining phase of SC23, with a peak in year Fig. Instead, we can look at the EEP impact by contrasting periods of maximum and minimum EEP activity, which is then an indication of the maximum variability during the solar cycle.
On the basis of the strength and frequency of the EEP Fig. Before the analysis, we carefully removed SPE-influenced periods from all data sets. For example, in November Fig. Subplots: winter time average ECRs between and Most studies have concentrated on the so-called indirect particle precipitation effect caused by the production of odd nitrogen NO x in the polar upper atmosphere, its subsequent transport to lower altitudes inside the wintertime polar vortex, depletion of ozone in the stratosphere and effects on the radiative balance of the middle atmosphere 10 , 11 , 12 , These effects may further couple to atmospheric dynamics and propagate downwards by changing polar winds and atmospheric wave propagation through wave—mean flow interaction 14 , 15 , Several studies have suggested links between the EPP indirect effect on ozone and regional wintertime tropospheric climate variability 17 , 18 , 19 , Our results show that the direct, HO x -driven effect of EEP is causing significant, previously unaccounted for, ozone variability in the mesosphere that are observable on solar cycle timescales.
Although these effects from EEP-HO x have not been considered in atmospheric and climate models to date, dynamical changes in the mesosphere and stratosphere have been reported as a result of SPEs and the indirect EEP impact on ozone 19 , Considering the magnitude of the direct ozone effect, tens of percent in wintertime polar regions, it is reasonable to suspect that EEP could be an important contributor to the Sun-climate connection on solar cycle timescales.
Thus, more research should be directed towards better understanding the potential further effects from EEP and its role in the overall Solar influence on climate. Currently, in most high-top climate models the solar input does not include EEP and it is completely missing from low-top models.
We use zonally averaged daily mean ozone profiles. Characteristics of these data sets are given below and in Supplementary Table 1. The anomalies in Figs 1b and 2 are calculated on a daily timescale with respect to a 7-day average before the EEPevent.
The starting point for each event is defined as the first day of an EEP event with geomagnetic Ap index exceeding By selecting this SZA limit, we have increased number of profiles selected but include some observations under twilight conditions. The MLS v3. We utilize data from L shells spanning 3. The precipitating ECRs measurements are considered the same way as in previous studies using the same data 2.
Superposed epoch analysis is used to test the significance of ozone loss because of energetic electron precipitation. For data set 1 Fig. For data set 2 Supplementary Fig.
For data set 3 Supplementary Fig. The analysis was carried out for each satellite and both hemispheres separately. How to cite this article : Andersson, M. Missing driver in the Sun—Earth connection from energetic electron precipitation impacts mesospheric ozone. Verronen, P. First evidence of mesospheric hydroxyl response to electron precipitation from the radiation belts.
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