Session 3 - Space Climate

Luke Barnard (University of Reading), Thierry Dudok de Wit (University of Orléans), Bernd Funke (Instituto de Astrofísica de Andalucía), Natasha Krivova (Max Planck Institute for Solar System Research), Kalevi Mursula (University of Oulu)
Monday 14/11, 14:30-17:00
Mercator

Observations of the Sun and heliosphere show that the solar magnetic field is dynamic over all observed temporal and spatial scales. In addition to the well-established Schwabe and Hale cycles of solar activity, there is much discussion about the causes, implications and predictability of solar variability on decadal and longer timescales. For example, what causes the occurrence of grand activity minima, such as the Maunder minimum, and can they be predicted with any skill? To answer such questions often requires the use of proxies of long-term solar activity, such as the sunspot, geomagnetic activity and cosmogenic isotope records, all of which have undergone significant developments in the last 2 years. Hopefully these recent developments of the historical space climate record will help us develop a deeper understanding of long-term solar activity and its predictability. Space climate research is further motivated by the growing understanding that the meteorology and climate of Earth respond in a complex but significant way to variations in direct solar forcings, such as TSI and SSI, as well as indirect solar forcings, such as the net energetic particle forcing from galactic cosmic rays, solar energetic particles and magnetospheric particles. Therefore, space climate is clearly a broad topic, involving many areas of solar physics and geophysics. Our aim is that this session will discuss the interesting new results from across the whole span of space climate research.

Poster Viewing
Monday November 14, 16:00 - 17:00, Poster Area

Talks
Monday November 14, 14:30 - 16:00, Mercator

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Talks : Time schedule

Monday November 14, 14:30 - 16:00, Mercator

14:30	Reconstructions of Solar Irradiance on the Millennial Timescale	Wu, C et al.	Invited Oral
	Chi-Ju Wu[1], Natalie Krivova[1], Sami K. Solanki[1,2], Ilya Usoskin[3]
	[1]Max Planck Institute for Solar System Research, Germany; [2]Kyung Hee University, South Korea; [3]University of Oulu, Finland
	Solar irradiance is by far the dominant energy source to Earth's climate system, and thus understanding of irradiance changes, especially on long timescales, is crucial for reliable assessment of solar influence on Earth's climate. On timescales of 11-year or shorter, solar irradiance is measured by space-based experiments while suitable models are needed for reconstructions over longer periods of time. Sunspot observations are commonly used as a proxy of solar activity over the last centuries. Going further back in time is only possible with cosmogenic isotope data, such as 14C and 10Be concentrations in terrestrial archives. In this talk we will discuss the most recent progress in reconstructions of solar variability and irradiance on the millennial timescale.
14:50	Drivers and Solar Cycles Trends of Extreme Space Weather Disturbances	Kilpua, E et al.	Invited Oral
	Emilia Kilpua
	University of Helsinki
	Coronal Mass Ejections are known to be the primary causes of the most extreme geomagnetic storms in the near-Earth Space. In this presentation I will discuss the perquisites for a CME to drive the most intense geospace disturbances based on the solar wind observations during two past solar cycles. I will also present statistics spanning over 13 solar cycles based in the extensive geomagnetic index AA data set and sunspot number recordings to characterize how the occurrence of extreme storms correlates with the strength of the solar activity cycle. The analysis shows that also quieter Sun can launch super-storms (e.g., Carrington storm in 1859) and suggests that extreme eruptions are related to the evolution of the toroidal component of the large-scale solar magnetic field.
15:10	Winds of winter: How solar wind driven energetic particles can affect northern winters	Maliniemi, V et al.	Invited Oral
	Ville Maliniemi, Timo Asikainen, Kalevi Mursula
	ReSoLVE Centre of Excellence, Space Climate Research Unit, University of Oulu, Finland
	Solar wind drives electromagnetic variability in the near Earth space. The coupling of solar wind and magnetosphere accelerates energetic particles in the magnetosphere, most of which typically get trapped into the dipolar field of the inner magnetosphere and a part is precipitating in the atmosphere. Long-lived high-speed solar wind streams (HSS) are more commonly observed at the Earth’s orbit during the declining phase of the solar cycle. HSSs effectively accelerate particles to high energies and lead to enhanced particle precipitation into the atmosphere. Energetic particles (tens to hundreds of keV) precipitate from the ring current down to the mesosphere where they can cause chemical changes and create nitrogen and hydrogen oxides. During winter, in polar night, the nitrogen oxides have enhanced lifetimes. They can then descend to the upper stratosphere and destroy ozone, which leads to the cooling of the lower stratosphere and increases temperature differences between the pole and low latitudes, enhancing westerly winds. These changes in the stratosphere can descend down to the troposphere and to the surface where they affect the large scale climate patterns, increasing the positive phase of the northern annular mode (NAM or North Atlantic oscillation, NAO) and intensifying the polar vortex. This closes the cold arctic air into the polar region and enhances the westerly winds at mid-latitudes. Enhancement of westerlies brings warm and moist air from Atlantic to the North Eurasia causing positive temperature anomalies. At the same time negative temperature anomalies are observed in the Northern Canada and Greenland. It has recently been shown that a positive relation exists during winter between precipitating particle fluxes/geomagnetic activity and NAM/NAO. Moreover, a positive NAO pattern is systematically observed during the declining phase of the solar cycle, when HSSs and energetic particle fluxes are maximized. These results give strong evidence that not only solar electromagnetic radiation but also the solar wind can affect the climate.
15:30	Evolution of Research on Long-term Solar Wind Magnetic Field Strength	Cliver, E et al.	Invited Oral
	Ed Cliver
	National Solar Observatory, Boulder, CO USA
	The solar wind has been directly observed for only ~50 years, so our knowledge of its long-term variation is limited. The past two decades have witnessed remarkable progress in overcoming this limitation. Beginning with the seminal paper by Lockwood et al. (1999) on the change in the Sun’s coronal magnetic field during the 20th century, key developments include the construction of new long-term geomagnetic indices, examination of the causes of differences between the Wolf and Group sunspot number time series, and extensions of high-time resolution cosmogenic-nuclide-based reconstructions of solar wind magnetic field strength (B). The multiple paths for inferring B (geomagnetic, sunspot, cosmogenic nuclide) and differing approaches among investigators led to a turbulent period of lively research. Recently, an ISSI International Team reported strong/reasonable convergence of solar wind B time series based on each of the three types of observations over the 1750-present interval (Owens et al., 2016a,b).
15:50	Cyclic activity and grand minima in solar-like stars	Brun, A et al.	Oral
	A.S. Brun[1], K. Augustson[1], M.S. Miesch[2], J. Toomre[3]
	[1]AIM, CEA-Saclay, France; [2]HAO, NCAR, USA; [3]JILA, Univ. Colorado, USA
	We will discuss how dynamo action in the Sun and solar-like stars can yields cyclic yet intermittent magnetic states. Based on multi-D MHD numerical simulation of rotating convection in solar-like stars we will show that the interplay between primary and secondary dynamo families in low magnetic Prandtl regime results in a large diversity of dynamo states akin to that of the Sun with extended period of minimal state of magnetic activity.

Posters

Monday November 14, 16:00 - 17:00, Poster Area

1	Uncertainties in the sunspot numbers: what do they tell us ?	Dudok de wit, T et al.	p-Poster
	T. Dudok de Wit[1], F. Clette[2], L. Lefèvre[2]
	[1]LPC2E, CNRS and University of Orléans, France; [2]Royal Observatory of Belgium
	Sunspot number series are subject to various uncertainties, which are still poorly known, and yet, are essential for their analysis. The need for their better understanding was recently highlighted by the major makeover of the international Sunspot Number. We present the first thorough estimation of these uncertainties, which behave as Poisson-like random variables with a multiplicative coefficient that is time- and observatory-dependent. We provide a simple expression for these uncertainties, and reveal how their discontinuous evolution in time coincides with changes in the observing strategy, and processing of the data. Knowing their value is essential for properly building composites out of multiple observations. We propose a strategy that bypasses backbones, and daisy-chaining.
2	Short-term variations of the sunspot number second differences as a predictor of the next cycle strength	Podladchikova, T et al.	p-Poster
	Tatiana Podladchikova[1], Ronald Van der Linden[2]
	[1]Skolkovo Institute of Science and Technology, Moscow, Russia; [2]Solar-Terrestrial Center of Excellence, ROB, Uccle, Belgium
	Forecasting of the strength of sunspot cycle is highly important for space weather applications. Our previous studies have shown the importance of short-term sunspot activity during the declining phase of cycle 23 that allowed us to predict the peak of cycle 24 with sunspot maximum not exceeding 72 (using sunspot number before the major change of data set on July 1st, 2015). However, the obtained prediction required knowledge of the sunspot minimum epoch between the cycles. In this study we demonstrate a clear relationship between short-term variations of the sunspot number second differences (SNSD) in the early stage of declining phase and the strength of next sunspot cycle when the minimum of current cycle has not yet occurred. To identify the stable regularities of SNSD we apply the optimal smoothing technique of monthly mean sunspot numbers. A relevant indicator is constructed from the found regularities of SNSD that determines if the strength of next cycle will be stronger or weaker compared to the current one and is validated by a perfect agreement for all the cycles 1-23. On the basis of this indicator, at the early stage of declining phase of cycle 24, we predict that the sunspot cycle 25 will be weaker than the current cycle 24.
3	Contribution of the geomagnetic activity monitoring by the Athens Space Weather Forecasting Center to the Hellenic National Meteorological Service	Paouris, E et al.	p-Poster
	Evangelos Paouris[1], Maria Gerontidou[1], Helen Mavromichalaki[1], Theodoros Kolydas[2], Ioannis Kouroutzoglou[2]
	[1]Faculty of Physics, National and Kapodistrian University of Athens, Athens, Greece; [2]Hellenic National Meteorological Service, Athens, Greece
	During the last years the Athens Space Weather Forecasting Center (ASWFC) provides a Space Weather report on a daily basis (http://cosray.phys.uoa.gr/index.php/space-weather-report) giving information about the solar activity, the solar wind geomagnetic activity, the solar energetic particle events (SEPs), the coronal holes (CHs) and a three-day geophysical activity forecast as well. It is noted that the disturbed periods and the recorded geomagnetic storms with their characteristics, such as the scale level and the origin of the storm (CME or CIR), are also determined. In this work an evaluation of the predicted results of the geomagnetic index Ap obtained from the Athens Space Weather Forecasting Center in comparison to the observed ones for the years 2014-2016, is presented. Furthermore, a statistical analysis of these events and a comparative study of the forecasting and the actual geomagnetic conditions using data from the NOAA space weather forecasting center and from the ASWFC as well are performed. Finally, a potential association of this Space Weather report to the products provided by the Hellenic National Meteorological Service is discussed.
4	Solar activity forecasting on decadal and longer timescales	Barnard, L et al.	p-Poster
	Luke Barnard[1], Thierry Dudok de Wit[2]
	[1]University of Reading; [2]LPC2E, CNRS and University of Orléans
	Currently there exist no skillful, physics based models of solar activity that can be used to provide useful predictions of solar activity on decadal and longer timescales. Therefore much effort has been invested into exploiting empirical relationships and utilising statistical techniques with different solar activity records, to produce forecasts and predictions of future solar activity. There is growing demand for knowledge of solar activity on decadal and centennial timescales, from, for example, space mission planning and Earth climate research. Much literature exists on solar activity forecasts on timescales up to the typical solar cycle timescale of 11 years. However there is significantly poorer understanding about the performance of solar activity forecasts on longer timescales. In this study we use several different centennial and millennial scale records of solar activity with a range of different statistical forecast techniques, to provide an assessment of the performance of these different techniques. Finally, given these different data sources and techniques, we assess whether there is any consensus about how solar activity is likely to change over the next century.
5	LYRA Mid-Term Periodicities	Wauters, L et al.	p-Poster
	Wauters L., Dominique M., Dammasch I.E.
	Royal Observatory of Belgium
	The spectra of the PROBA2/LYRA data, similarly to every other solar time series, show predominant periodicities that can be of solar or of instrumental origin. We compare the main periodicities characterizing the LYRA spectrum to the ones found in the sunspot number, in the 10.7 cm flux, in a X-ray flare index, and in the sunspot area evolution. We mainly focused on the 2010 to 2014 time-range, for which the LYRA data are available, although we also briefly address the evolution of the main periodicities in the longer range. The mid-term periodicities at ~28, ~44, ~54, ~59, ~100, ~110, ~150 days appear as highly significant in several analyzed datasets. The consistency of distinct periodicities between datasets provides characteristics for the global Sun. This consistency also strengthens the robustness of LYRA data.